Drive device

ABSTRACT

The invention relates to a drive device comprising an electric drive motor, a housing, at least one shaft driven by the drive motor, compensation means enabling the end play of the shaft to be adjusted or compensated while the shaft is being mounted, and fixing means which are used to the shaft after the end play has been adjusted or compensated. The invention is characterised in that the compensation means comprise a spring element which is arranged inside the housing and which axially actuates the shaft, and that the fixing means are not accessible from the outer side of the housing.

[0001] The invention relates to a drive device having an electric drivemotor, having a casing, having at least one shaft driven by the drivemotor, with compensating means with which an adjustment of orcompensation for end play of the shaft can be made when installing theshaft and with securing means with which the shaft is secured after endplay has been adjusted or compensated for. The invention also relates toa method of installing a drive device of this type.

[0002] The shaft driven by the drive motor is understood to mean in whatfollows an output shaft driven by the drive motor through a gear,specifically through a worm gear, as well as an armature shaft drivendirectly by the drive motor.

[0003] Drive devices of this type find an application particularly inthe automotive industry as servo motors for seat adjusters, steeringcolumn adjusters, window regulators, sliding sunroofs or similar, and asdrive devices for windshield wiper systems. The drive devices normallyhave a worm gear attached to the drive motor, which advantageously hassmall dimensions, can transmit high levels of power and is self-locking.

[0004] Specifically because of the tapered flanks of the worm and theworm wheel in a worm drive of this type, an axial force acts on thearmature shaft of the drive motor during operation of the drive device,as well as on the output shaft of the worm drive. The direction of theaxial force depends on the direction of the armature shaft's rotation.With a change in direction of the drive motor or a change in externalload, the direction of the axial force on the armature shaft as well ason the output shaft is reversed. During the installation of a shaft ofthis type, it is of special importance to adjust the end play precisely,or to compensate for the end play, so that the shafts are carried freeof end play. If the shafts of drive devices of this type are installedwith end play, abrupt starting motions and irritating noises result whenthe drive motor reverses direction. Furthermore, noticeable relativemotions can result if the servo motor is employed as a seat backadjuster, for example. The person occupying the particular seatperceives the end play as relative movement of the seat back, even whenthe motor of the drive device is not running. This phenomenon isadditionally known in the case of steering column adjusters. End playthat is present can additionally lead to uneven loading on the shaft,and on the worm and worm wheel, causing malfunctions of the drivedevice.

[0005] A worm drive is known from DE 198 24 382 A1 in which the end playis adjusted during assembly by means of a pin projecting from thehousing of the drive device. A pin of this type is then swaged to thehousing after the end play is adjusted.

[0006] The prior art of this type has the disadvantage that compensationfor, or adjustment, of the end play is complicated to perform. An extradevice is required which exerts a force from the outer side of thehousing on the end bearing carrying the shaft by way of thecorresponding pin. In addition, because of the opening extending throughthe housing to receive the pin, problems can arise with the sealing ofthe worm drive.

[0007] The object of the present invention is therefore to eliminate thedisadvantages of the previously enumerated disadvantages of the priorart.

[0008] This object is achieved in the case of a drive device of the typedescribed initially in accordance with the invention, in which thecompensating means comprise a spring element located inside the housingand impinging axially on the shaft, and the securing means are notaccessible from the outer side of the housing. By reason of a springelement of this type it is possible to assemble the shaft under axialpre-load. Compensating means in accordance with the prior art whicheffect compensation for, or adjustment of, the end play from the outerside of the housing are rendered unnecessary. As a result of thecompensating means being located inside the housing in the form of aspring element, no breakthrough in the housing is required to achieveadjustment of or compensation for end play. Advantageous provision isalso made under the invention for the securing means not to beaccessible from the outer side of the housing, whereby no breakthroughin the housing is required to secure the securing means. A housingwithout such breakthroughs can be produced particularly cost-effectivelyin series production because corresponding work operations which arenecessary under the prior art are redundant. Furthermore, no problemsarise with sealing a housing of this type which has no breakthroughs.Consequently under the invention measures to seal the housing areredundant.

[0009] In an advantageous embodiment of the invention, the springelement is supported against the housing. This dispenses with the needfor additional components which receive and redirect the force of thespring into the housing.

[0010] In another particularly advantageous embodiment of the inventionthe spring element impinges on a pressure ring which bears against theouter race of a bearing, specifically a roller bearing, which isprovided to carry the shaft. The outer race is axially moveable withrespect to the housing, or the bearing section of the housingrespectively, to provide relative movement of the bearing with respectto the housing. Through the bearing, or the inner race, an axial forceis exerted on the shaft, which results in compensation for end play.

[0011] Advantageous provision can be made for the pressure ring to havea shaft-like flange which can be secured to the housing as acompensating means, wherein the shaft-like flange is enclosedspecifically by a closed, cup-shaped section of the housing in the finalassembly position. After compensating for or adjusting end play, theshaft-like flange can be secured to the housing by reason of the axialforce exerted by the spring element on the shaft bearing, or on theshaft respectively.

[0012] Securing can be advantageously effected by staking the securingmeans, the shaft-like flange for example, to the housing.Circumferential staking is one possibility, as well as a 4- or 6-punchstaking. Alternatively it is also conceivable to weld the securing meansto the housing.

[0013] In a particularly advantageous embodiment of the invention, thespring element is a spring washer mounted on the shaft, specifically adiaphragm spring washer. A spring washer of this type can be installedto economize on space and demonstrates suitable spring characteristics.

[0014] A further embodiment of an inventive drive device ischaracterized in that the drive device can be assembled axially from oneside. This is of great advantage particularly in series production,since assembly in this manner can be implemented easily and saves costs.

[0015] In accordance with the invention the shaft can be an input shaftdriven by the drive motor through a gear, specifically a worm gear, orcan also be an armature shaft driven directly by the drive motor.

[0016] The object stated initially is also achieved through a procedureto assemble a drive device, which provides for a free end of the shaftto be inserted into the pre-installed bearing which is supported againstthe housing, for the outer race of the bearing to be pressed against thepressure ring by reason of the end displacement of the shaft, where thepressure ring has a shaft-like flange facing away from the direction ofinstallation, and for the pressure ring to be impinged on by an axialspring force from the spring element exerted counter to the direction ofinstallation and for the shaft-like flange to be secured to the housingin the final installed position of the shaft, specifically to be stakedto a closed cup-shaped section of the housing enclosing the flange. Anassembly procedure of this type has the advantage that adjustment of orcompensation for end play is carried out automatically. Furthermore, thesecuring of the shaft position can be carried out from outer side of thehousing. Overall, assembly of this kind can be accomplished simply andin a cost-effective manner.

[0017] Additional advantageous embodiments and particulars of theinvention can be found in the description to follow, in which theinvention is described and explained in greater detail with reference tothe embodiment shown in the drawing.

[0018]FIG. 1 shows a schematic representation of a drive device inaccordance with the invention in a longitudinal section in the finalinstalled position,

[0019]FIG. 2 shows an enlarged view of the section identified in FIG. 1by X, and

[0020]FIG. 3 shows the drive device from FIG. 1 in its pre-installationposition.

[0021] The drive device 1 shown in FIG. 1 has a housing which basicallycomprises two housing sections, specifically a housing base 3 and ahousing cover 4. The drive device further has a drive motor 5, whichcomprises a stator 6 located on the housing base 3 as well as anarmature 8 located on a shaft 7, specifically the armature shaft. Inaddition, a collector 9 is shown schematically on the armature shaft 7.Two roller bearings 12 and 13 are provided to carry the shaft 7.

[0022] The free end 14 of the shaft 7 projecting from the housing cover4 has a worm 15 to drive a worm wheel, which is not shown.

[0023] To ensure permanent, trouble-free operation of such a drivedevice, it is necessary to assemble the drive device 1 in such a waythat the shaft 7 is ideally installed without end play. Because of thebeveled teeth on the worm 15, high axial forces occur when the shaft 7changes direction. If a drive device 1 of this type exhibits end play inthe assembled state, after a short time it results initially in annoyingnoise during operation. With continued operation, this end play can leadto operating malfunctions and to failure of the drive device 1.

[0024] As compensating means to adjust or the compensate for end play, aspring element, specifically a diaphragm spring washer 18, which can beseen clearly in FIG. 2., is provided inside the housing base 3. Thespring washer 18 is located on a shaft-like flange 25 and is supportedagainst the housing base 3. The spring washer 18 imposes an axial springforce against a pressure ring 19 formed in one piece with the flange 25,said ring in turn impinging on the outer race 20 of the bearing 12. Theshaft-like flange 25 facing away from the shaft 7 is received by aclosed, cup-shaped section 26, or is enclosed by said section. The fitbetween the outer race 20 and the area of the housing base 3 surroundingthe outer race 20 is selected such that axial displacement of thebearing 12 is possible by reason of the spring force being exerted onthe outer race 20 through the pressure ring 19. The inner race 22 of thebearing 12 acts axially against a lock ring 23 positively located on theshaft, said ring transferring the force emanating from the springelement 18 into the shaft 7. By reason of the axially exerted springforce emanating from the spring washer 18, there is subsequently axialimpingement on the shaft 7 through the pressure ring 19, the bearing 12and the lock washer 23. The end play of the shaft 7 is thereby adjustedor compensated for during the installation process. However, it must bepointed out that the axial spring force from the spring washer must notbe so high that the bearing 12, or the outer race 20 compared with theinner race 22, is subjected to excessive axial loading. Loading of thistype can lead to high bearing wear and ultimately to failure of thebearing 20.

[0025]FIG. 3 clearly illustrates the assembly procedure for the drivedevice 1. First, the pressure ring 19 with shaft-like flange 25 and thespring washer 18 installed over it is inserted into the cup-shapedsection 26 of the housing base 3. Further, the bearing 12 is pushed intothe bearing section 24 of the housing base 3 provided for it. As can beseen clearly from FIG. 3, the sides of the pressure ring 19 facing thebearing 12 are spaced from the bearing 12.

[0026] At the same time, the housing cover 4 can be assembledindependently thereof to the bearing 13 which is supported against thehousing cover 4 and the armature shaft 7, which carries the armature 8and the collector 9. A brush mounting plate, for example, withappropriate brushes and other components can be assembled to the housingcover 4.

[0027] In a subsequent operation, the end of the shaft carrying thelocking ring 23 can be inserted axially into the bearing 12 in thedirection of the arrow 27. The locking ring 23 is thereby brought up tothe inner race 22 of the bearing 12 and the entire bearing 12 in thebearing section 24 is pushed axially in the direction of the pressurering 19. If the shaft 7 is moved further in the axial direction, thepressure ring is impacted with a spring force by reason of the springwasher 18, which acts against the direction of installation 27. When theshaft 7 reaches its final installation position, which is shown in FIG.1, the shaft 7 is then rides without end play between the two bearings12 and 13.

[0028] In a further operation, the shaft-like flange 25 is secured tothe cup-shaped section 26 of the housing base 3. When it is secured, thesecured means, specifically the shaft-like flange 25, is not accessiblefrom the outer side of the housing in accordance with the invention.Advantageously, a breakthrough in the housing base 3, or the cup-shapedsection 26, is not required to secure the shaft-like flange 25. As aresult of there being no provision for breakthroughs in the housing base3 and the cup-shaped section 26 to adjust or compensate for end play orto secure the shaft-shaped flange 25, no undesirable media such ashumidity, dust or dirt can penetrate to the interior of the drive device1. A drive device 1 of this type is therefore sealed against externalinfluences.

[0029] The shaft-like flange 25 is preferably staked to the cup-shapedsection 26 along the arrows 28 shown in FIG. 1 and 2. This staking cantake the form of circumferential staking. It is also conceivable tostake it at 4 or 6 points. In order to achieve a definite deformation ofthe section 26 and the flange 25 during the staking procedure, thesection 26 and the flange 25, as shown in FIG. 2 can have annulargroove-like notches. Instead of staking, it is also conceivable tosecure section 26 with the flange 25 by means of welding after end playhas been adjusted and thus connect them immovably.

[0030] After securing, advantageously no axial forces act upon the shaft7 which rides without end play. Since the spring washer. 18 ispositioned under pre-load between the housing and the pressure ring, noirritating noises, in particular rattling noises can emanate from thespring washer 18 captured in this way, even during later operation ofthe drive device 1.

[0031] As is clear from FIG. 3 and the attendant description, the drivedevice 1 in accordance with the invention can be assembled axially fromone side. This results in enormous cost savings, particularly in volumeseries production.

[0032] In the embodiment shown and described, the shaft 7 is an armatureshaft. It is also conceivable that a shaft driven by a gear,specifically by a worm gear, can be assembled in a similar mannerwithout end play.

[0033] As a result of the cup-shaped section 26 having a closedconfiguration, machining operations, which are required in accordancewith the prior art, are also not necessary. The adjustment of end play,or the compensation for end play, can be performed without any steps oradjustments from outside; adjustment or compensation for end play takesplace automatically. No additional adjustment procedure is needed.

[0034] All the features shown in the description, the claims to followand the drawing can be essential to the invention both individually andin any combination together.

What is claimed is:
 1. Drive device (1) with an electric drive motor(5), having a housing (3, 4), at least one shaft (7) driven by the drivemotor (5), with compensating means with which end play in the shaft (7)can be adjusted or compensated for and with securing means with whichthe shaft (7) can be secured following adjustment of or compensation forend play, characterized in that the compensating means comprise a springelement (18) located inside the housing (3, 4) exerting axial force onthe shaft (7) and that the securing means (25) are not accessible fromthe outer side of the housing.
 2. Drive device (1) from claim 1, whereinthe spring element (18) is supported against the housing (3).
 3. Drivedevice (1) from claim 1, or 2, wherein the spring element (18) bearsagainst a pressure ring (19) which impinges on the outer race (12) of abearing (12), specifically a roller bearing, which carries the shaft(7).
 4. Drive device (1) from claim 1, 2 or 3, wherein the pressure ring(19) has a shaft-like flange (25) which can be secured to the housing(3) as a securing means, where the shaft-like flange (25) is enclosed bya closed, cup-shaped section (26) of the housing (3) in the finalinstallation position.
 5. Drive device (1) from one of the precedingclaims, wherein the securing means (25) are staked to the housing (3).6. Drive device (1) from one of the preceding claims, wherein the springelement is a spring washer, specifically a diaphragm spring washer (18),positioned on the shaft.
 7. Drive device (1) from one of the precedingclaims, wherein the drive device (1) can be assembled axially from oneside.
 8. Drive device (1) from one of the preceding claims, wherein theshaft (7) is an output shaft driven by the drive motor through a gear,specifically through a worm.
 9. Drive device (1) from one of thepreceding claims, wherein the shaft (7) is an armature shaft driven bythe drive motor (5).
 10. Procedure to assembly a drive device (1) fromone of the preceding claims, characterized in that a free end of theshaft (7) is inserted into the pre-assembled bearing (12) which issupported against the housing, that the outer race of the bearing ispressed against the pressure ring (19) by reason of the axialdisplacement of the shaft (7), where the pressure ring (19) has ashaft-like flange (25) away from the direction of assembly, that thepressure ring (19) is impacted by an axial spring force from the springelement (18) working against the direction of installation and that inthe final installation position of the shaft (7) the shaft-like flange(25) is secured to the housing and is specifically staked to a closedcup-shaped section (26) of the housing (3) surrounding the flange (25).